Integration of annealing capability into metal deposition or CMP tool

ABSTRACT

Integration of annealing capability into a metal deposition tool or a chemical mechanical polishing (CMP) tool. A wafer processing apparatus includes a metal deposition tool having annealing capability. The metal deposition tool can be an electroplating tool or a chemical vapor deposition tool or other metal deposition tool that deposits metal films, such as copper, onto silicon substrates for integrated circuit manufacturing. An annealing chamber is integrated into the metal deposition tool so that annealing of the metal film can be controlled such that the copper is consistently stabilized in preparation for a chemical mechanical polishing process. Alternatively, an annealing chamber can be integrated into a CMP tool.

FIELD OF THE INVENTION

[0001] The present invention relates generally to semiconductormanufacturing and, in particular, to the integration of annealingcapability into metal deposition tools or chemical mechanical polishingtools.

BACKGROUND OF THE INVENTION

[0002] In integrated circuit manufacturing processes, it is generallydesirable to minimize the total number of steps in the process and thetime between each step. While it is generally desirable to allow thegreatest latitude in fabrication process parameters, in certain cases,known variations can be eliminated or controlled to an extent thatprovides a greater predictability of results of the process. One suchvariation occurs during the stabilization of metal films that aredeposited on a wafer dielectric layer to form interconnects betweenactive devices.

[0003] Integrated circuits (ICs) manufactured today generally include anelaborate system of metalized interconnects to couple the variousdevices that have been fabricated in the semiconductor substrate. Thetechnology for forming these metalized interconnects is extremelysophisticated. Commonly, aluminum, copper or some other metal isdeposited on a dielectric layer and then patterned to form interconnectpaths. Another dielectric or insulation layer such as silicon dioxide(SiO₂) is then deposited over this first metal layer (metal 1); viaopenings are etched through the dielectric layer; and the second metallayer (metal 2) is deposited. The metal 2 layer covers the dielectriclayer and fills the via openings, making electrical contact down to themetal layer. After a metal layer is deposited, the layer is usuallyplanarized in a chemical mechanical polishing (CMP) process to removethe portions of the metal layer that do not form the desiredinterconnects such as lines or vias.

[0004] A considerable amount of effort in the manufacturing of moderncomplex, high density, multilevel interconnections is devoted to theplanarization of the individual layers of the interconnection structure.Nonplanar surfaces create poor optical resolution of subsequentphotolithographic processing steps. Poor optical resolution prohibitsthe printing of high density lines. Another problem with nonplanarsurface topography is the step coverage of subsequent metalizationlayers. If a step height is too large there is a serious danger thatopen circuits will be created. Planar interconnect surface layers are amust in the fabrication of modern high density multilevel integratedcircuits.

[0005] CMP employs polishing to remove protruding steps formed along theupper surface of the inter-layer dielectric. CMP is also used to “etchback” deposited metal layers to form planar plugs or vias. In a typicalCMP process, a silicon substrate or wafer is placed face down on arotating table or platform covered with a flat polishing pad that hasbeen coated with an active slurry. A carrier, which is typically made ofa thick, nonflexible metal plate, is used to apply a downward forceagainst the backside of the substrate. The downward force and therotational movement of the pad together with the slurry facilitate theabrasive polishing and planar removing of the upper surface of the thinmetal film.

[0006] Nonuniform polishing can result in too much film being removedfrom some parts of the wafer and not enough film being removed fromother parts. Also, lack of uniformity in the polishing rate from waferto wafer can result in decreased process yield and reliability.Significant effort has been expended in attempts to control thepolishing part of the process of integrated circuit manufacturing.

[0007] Electroplating is becoming the favored technique at least forcopper deposition in the semiconductor industry. Electroplated copper,however, is known to be unstable at room temperature. Its physicalproperties such as resistivity and hardness continue to change withtime. This process can last for weeks and can have significant impact onthe stability of the subsequent process steps such as CMP. Annealing canaccelerate the stabilization of the copper film, but adds an additionalstep in the process flow. Also, when annealing is performed by aseparate annealing tool, the time between the deposition of the copperor metal layer can vary due to any number of reasons, such asunavailability of the annealing tools, imprecise scheduling or aphysical distance between the annealing tool and the CMP tool.

[0008] Changes in the resistivity and hardness of the metal that hasbeen deposited can affect the rate of polishing during the CMP portionof the process. It is desirable to minimize the variability of thestabilization of the metal. Annealing helps to stop the degradation orchange in the properties of the metal. If the deposited metal isstabilized consistently, greater predictability can be achieved in theCMP process.

SUMMARY OF THE INVENTION

[0009] In one embodiment, an apparatus includes a metal deposition toolhaving annealing capability.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

[0011]FIG. 1 is a schematic representation of a prior art waferprocessing apparatus;

[0012]FIG. 2 is a schematic representation of an embodiment of a waferprocessing apparatus;

[0013]FIG. 3 is another embodiment of a wafer processing apparatus;

[0014]FIG. 4 is yet another embodiment of a wafer processing apparatus;

[0015]FIG. 5 is a top plan view of one embodiment of a wafer processingapparatus; and

[0016]FIG. 6 is a top plan view of another embodiment of a waferprocessing apparatus.

DETAILED DESCRIPTION

[0017] A wafer processing apparatus including a metal deposition toolhaving annealing capability is described. Examples of metal depositiontools are electroplating tools or chemical vapor deposition (CVD) tools.The integration of annealing capability into a metal deposition tool canresult in better control over the stabilization of the metal prior to asubsequent process such as chemical mechanical polishing (CMP).Alternatively, annealing capability can be integrated into the CMP tool.

[0018]FIG. 1 is a schematic representation of a wafer processingapparatus 100 of the prior art. Electroplating tool 110 includes atleast one, and usually a plurality, of electroplating chambers 112. Awafer is processed through wafer processing apparatus 100 by firsthaving a metal such as copper deposited onto a dielectric layer of thesilicon substrate in one of the electroplating chambers 112. Typically,a batch or a plurality of wafers is processed in the electroplating tool110 at the same time.

[0019] After electroplating, the wafer is moved to an annealing tool 130that includes an annealing chamber 132. Annealing chambers can typicallybe a furnace that heats the wafer including the metal deposited on it bythe electroplating process. The annealing process is performed in orderto stabilize the electroplated or otherwise deposited metal. Theannealing is typically done in preparation for the CMP process duringwhich a portion of the metal is polished away. If the metal film is notstable, however, the polishing rate of the CMP process can beunpredictable. For example, because the hardness of the metal film canvary from wafer to wafer, it can be very difficult to determine how muchpolishing is adequate.

[0020] After the-annealing process, the wafer is transferred to a CMPtool 120. As shown in FIG. 1, CMP tool 120 can include a plurality ofCMP platforms 122. CMP platforms are typically rotating tables thatinclude a rotating pad on which the wafer rests during polishing.

[0021] Currently, copper is becoming a preferred metal for use inelectroplating interconnects on silicon wafers. Other metals such asgold or silver can also be deposited by electroplating. In the past, theelectroplating of copper was used mostly for decorative purposes. Assuch, the stability of the copper film was not a concern.

[0022] The resistivity of the copper film can be measured in an attemptto determine whether and to what extent the microstructure of the copperfilm has changed. Measuring the resistivity can indicate whether themicrostructure, for example the grain size or crystal orientation, ofthe copper has changed. Directly measuring grain size or crystalorientation requires destructive tests that are not easily performed ina manufacturing setting.

[0023] It is desirable to make the wafer manufacturing process moreefficient by eliminating any potential causes of change. For instance,since electroplated copper is unstable at room temperature, itsproperties tend to change over time. The change in the properties suchas hardness or resistivity increases the variability of the polishingrate during CMP because the copper film is not at the same level ofhardness, for example, every time for every wafer when polishing begins.It is desirable to stabilize the film by annealing before CMP. If theannealing is not performed shortly after the copper has been depositedby either electroplating or chemical vapor deposition (CVD), however,there is unpredictability in the properties of the copper film becauseof the lapse of time between the metal deposition process and annealing.During the time that has elapsed between these two steps, the copperfilm tends to change. If the annealing is not performed consistently, itis difficult to predict the rate of polishing that is necessary toachieve the desired results.

[0024] During electroplating, the wafer is placed into a solutioncontaining sulfuric acid and other additives that may include metalparticles such as copper. The electroplating tank has a cathode and ananode dipped into the solution. The anode can be made of copper. Duringthe electroplating process, metal particles within the solution (or fromthe anode as it dissolves) are deposited on the surface of a dielectriclayer of the silicon substrate. The copper particles fill small featuressuch as holes, lines or trenches that have been formed in the dielectriclayers on the substrate. After the copper is deposited, CMP is performedto remove the copper that is not needed down to a pre-selected planeleaving interconnects between different devices on the substrate.

[0025] When copper film is deposited by electroplating or CVD, there canbe outgassing for a period of time. Annealing can stabilize outgassing.During the annealing process, the metal deposited by electroplating orCVD is heated to temperatures of 50 to 400 degrees Celsius. Typically,about 200 degrees Celsius is the temperature at which annealing isperformed. The time for annealing can vary from about 1 to about 60minutes depending on the temperature used. Typically, the higher thetemperature, the shorter the time necessary to achieve stabilization ofthe metal by annealing.

[0026]FIG. 2 shows one embodiment in which a wafer processing apparatus200 includes a metal deposition tool and a CMP tool. The metaldeposition tool shown in FIG. 2 is an electroplating tool 210 that hasmultiple electroplating chambers 212. FIG. 2 shows a schematicrepresentation of an annealing chamber 232 on the electroplating tool210.

[0027] Annealing chamber 232 can be attached to or added ontoelectroplating tool 210 Alternatively, electroplating tool 210 can bemodified such that one of its plurality of electroplating chambers 212is replaced by annealing chamber 232. More than one annealing chamber232 can also be provided. Annealing chamber 232 can be a furnace (notshown) or can include heat lamps (not shown) or a hot stage (not shown).

[0028] CMP tool 220 is shown in FIG. 2 as having multiple CMP platforms222. Alternatively, multiple CMP tools 220 can be provided for apparatus200 or a single CMP tool 220 can provide a single CMP platform 222.

[0029]FIG. 3 shows another embodiment in which a wafer processingapparatus includes a metal deposition tool that is a chemical vapordeposition (CVD) tool 340. Also, apparatus 300 includes a CMP tool 320.

[0030] CVD tool 340 includes multiple CVD chambers 342. Annealingchamber 332 is provided on CVD tool 340. Annealing chamber 332 can beattached to-or can replace a CVD chamber 342 of CVD tool 340. A waferbeing processed will have a metal such as copper deposited by CVD in oneof the CVD chambers 342. After the metal deposition process, the waferis moved to annealing chamber 332, which is provided on CVD tool 340.Because annealing chamber 332 is integrated into CVD tool 340, theannealing process can begin almost immediately to avoid the degradationof the deposited metal. After the wafer has undergone annealing in theannealing chamber 332, it is transferred to the CMP tool 320 and ontoone of the CMP platforms 322.

[0031]FIG. 4 shows yet another embodiment in which a wafer processingapparatus 400 includes a metal deposition tool 460 and a CMP tool 420.In the embodiment shown in FIG. 4, metal deposition tool 460 includesmetal deposition chambers 462. Metal deposition tool 460 can be anelectroplating tool or a CVD tool, for example. Also, a metal depositiontool need not have multiple metal deposition chambers 462. Annealingchamber 432 is integrated into the CMP tool 420 in the embodimentillustrated in FIG. 4. CMP tool 420 includes CMP platforms 422. Duringprocessing, the wafer is transferred from metal deposition tool 460 intoannealing chamber 432, which is on CMP tool 420 in this embodiment.After annealing in annealing chamber 432, the wafer is transferredalmost immediately to a CMP platform 422 to undergo the CMP process. Inthis case, the amount of time between the end of the annealing processand the beginning of the CMP process can be controlled.

[0032] Alternatively, annealing can be performed after CMP to influencethe final properties of the metal. The apparatus 400 of FIG. 4 can alsoprovide this capability. Annealing before CMP can influence themicrostructure of the metal layer quite differently than annealing afterCMP because more metal is present before CMP. Annealing can cause thegrain to grow differently due to the presence of more or less material.

[0033]FIG. 5 shows an embodiment in which a wafer processing apparatus500 includes a metal deposition tool 560 and a robot 550 on the metaldeposition tool 560. Metal deposition tool 560 includes a plurality ofmetal deposition chambers 562. As described above, metal deposition tool560 can be an electroplating tool or a CVD tool, or any other type oftool that deposits metal onto the dielectric layer of a siliconsubstrate in the manufacture of integrated circuit devices.

[0034] Robot 550 moves a wafer 502 from a metal deposition chamber 562to an annealing chamber 532. Annealing chamber 532 is shown on metaldeposition tool 560. FIG. 5 illustrates an embodiment in which annealingchamber 532 can be provided as part of metal deposition tool 560 ormetal deposition tool 560 can be modified such that annealing chamber532 replaces a metal deposition chamber 562.

[0035] Alternatively, wafer processing apparatus 500 can include anannealing chamber that is on a CMP tool. In this case, robot 550 wouldmove the wafer 502 from the annealing chamber 532 into a CMP chamber orvice versa. It is preferred that annealing be performed before CMP inorder to stabilize the metal that was deposited onto the wafer, thusproviding more predictability in the CMP process. Alternatively,annealing can be performed after CMP to influence the final propertiesof the metal.

[0036]FIG. 6 shows an embodiment in which wafer processing apparatus 600includes a metal deposition tool 660 (or, alternatively, a CMP tool) andan annealing chamber 632 attached to the side of metal deposition tool660. In FIG. 6, metal deposition tool 660 includes a plurality of metaldeposition chambers 662. Annealing chamber 632 can be provided adjacentto metal deposition tool 660 and its metal deposition chambers 662.Robot 650 is also provided to move wafer 602 between metal depositionchambers 662 and annealing chamber 632.

[0037] An embodiment of a wafer processing method includes depositing ametal onto a substrate such as a wafer in a metal deposition chamber ofa metal deposition tool. The substrate is then moved from the metaldeposition chamber directly to an annealing chamber. Preferably, theannealing chamber is part of the metal deposition tool. The annealingprocess includes heating the metal in the annealing chamber. The methodcan include a metal deposition tool that is an electroplating toolhaving at least one electroplating chamber. The method alternatively caninclude a metal deposition tool that is a chemical vapor deposition(CVD) tool having at least one CVD chamber. Preferably, the methodincludes annealing or heating the wafer including the deposited metalbefore chemical mechanical processing (CMP) of the substrate isperformed.

[0038] Alternatively, a wafer processing method can include depositing ametal onto a substrate in a metal deposition chamber of a metaldeposition tool, moving the substrate from the metal deposition tool toan annealing chamber that is part of a chemical mechanical polishing(CMP) tool, heating the metal in the annealing chamber, moving thesubstrate from the annealing chamber to a CMP platform on the CMP tooland polishing the substrate including the metal after annealing.

[0039] Yet another alternative embodiment of a wafer processing methodcan include depositing a metal onto a substrate in a metal depositionchamber of a metal deposition tool; moving the substrate from the metaldeposition tool to a chemical mechanical polishing (CMP) platform on aCMP tool; polishing the substrate including the metal; moving thesubstrate from the CMP platform to an annealing chamber, wherein theannealing chamber is part of the CMP tool; and heating the metal in theannealing chamber. In this case, annealing can be performed after CMP.

[0040] Yet another alternative embodiment can include annealing beforeand after CMP. This embodiment can include an annealing-chamber on boththe metal deposition tool and on the CMP tool of a wafer processingapparatus.

1. An apparatus comprising: a metal deposition tool having annealingcapability.
 2. The apparatus of claim 1 further comprising an annealingchamber on said metal deposition tool.
 3. The apparatus of claim 2wherein said metal deposition tool is an electroplating tool.
 4. Theapparatus of claim 2 wherein said metal deposition tool is a chemicalvapor deposition (CVD) tool.
 5. The apparatus of claim 1 wherein saidmetal deposition tool has a plurality of metal deposition chambers, saidmetal deposition tool being modified to replace one of said metaldeposition chambers with an annealing chamber.
 6. The apparatus of claim5 wherein said metal deposition tool is an electroplating tool and saidmetal deposition chamber is an electroplating chamber.
 7. The apparatusof claim 5 wherein said metal deposition tool is a chemical vapordeposition (CVD) tool and said metal deposition chamber is a chemicalvapor deposition (CVD) chamber.
 8. The apparatus of claim 1 wherein saidmetal deposition tool includes at least one metal deposition chamber andan annealing chamber on said metal deposition tool.
 9. The apparatus ofclaim 8 wherein said metal deposition tool is an electroplating tool andsaid metal deposition chamber is an electroplating chamber.
 10. Theapparatus of claim 8 wherein said metal deposition tool is a chemicalvapor deposition (CVD) tool and said metal deposition chamber is achemical vapor deposition (CVD) chamber.
 11. The apparatus of claim 8wherein said annealing chamber includes heat lamps.
 12. The apparatus ofclaim 8 wherein said annealing chamber is a furnace.
 13. The apparatusof claim 8 further comprising a robot, wherein said robot moves a waferfrom said metal deposition chamber to said annealing chamber.
 14. Anapparatus comprising: an chemical mechanical polishing (CMP) tool havingannealing capability.
 15. The apparatus of claim 14 further comprisingan annealing chamber on said CMP tool.
 16. The apparatus of claim 14wherein said CMP tool has a plurality of CMP platforms, said CMP toolbeing modified to replace one of said CMP platforms with an annealingchamber.
 17. The apparatus of claim 14 wherein said CMP tool includes atleast one CMP platform and an annealing chamber on said CMP tool. 18.The apparatus of claim 14 wherein said annealing chamber includes heatlamps.
 19. The apparatus of claim 14 wherein said annealing chamber is afurnace.
 20. The apparatus of claim 14 further comprising a robot,wherein said robot moves a wafer from said annealing chamber to said CMPplatform. 21.-30. (Cancelled)